Apparatus for the production of gaseous mixtures



Nov. 19, 1935. R. w. THOMAS APPARATUS FOR THE PRODUCTION OFGASEOUS.,.MIXTURES Filed Feb. 18, 1930 Patented Nov. 19, 1935y PATENToFFicE mauri-Is iron 'rms monUc'rloN or Gase-ous mx'ruaas PhillipsPetroleum uw. Themenwelt, nimma Okla., a corporation oi' l man is,1m.sm1ro. 429,311

4cm. icl. isfiso) This invention 'to an improved and apparatus formanufacturing gas for use in smalltownsorthelilre.4 The large initialinstallation investment and :5 the high gas manufacturing cost o! gasplants or the conventional types for small properties,-are

such that from an economic point of view, such plants are notattractive. Even with high gas l rates, thenmajority of smallpropertiesv do not 1o show a reasonable'investment return. That; the

utility companies have not entered this field more fully is shown by thefact thatat the be- Aginning o! 1929, there were over two hundred citiesin the United States having infex'csof 15- five thousand people whichare .not supplied present in natural gasVoier veryinterestingpossibilities,v asrthe sole raw materials` in the 25manufacture of gas, particularly in locations that do not demand asupply in excess of 200,000 cubic `feet of gas per day.

The hydrocarbon fuel most available, plentie ful and economical topurchase, transfer, store 30 and use', is commercial butane.' It hasbeen Afound from the use oi charts dealing with the vaporpressure-temperature relations for various paramn hydrocarbons, theproperties of liquid commercial butaneare such that at pre- 35 vailingtemperatures, its vapor pressures are not excessive, therebyfacilitating the handling and the storage of 'the same, as a liquid,while at the same the vapor pressures are suili- .ciently high toinsure. against the condensation 40 of the commercial butane componentinthe finished gas,` even at low temperatures and high pressures. l

" By means of a' of commercial butane and non-condensible gases,

I T15 it is possibleto determine the condensation temperatures andpressures of mlxed'gases of vary-- ing composition. For example. it canbe'round by such a curve what the maximum per cent oi commercial butanein a mixed gas at .125 lbs. gauge, and 10 Fahrenheit, beforecondensation occurs. The percentage will be about 1.5 in this instance.On th`e other hand, by such a curve,

l.it is also possible to iind the condensation`point.

55- of a mixture having 17,5% o! butane no heating value, suchas nue Ylatter is universally available, and its use offers 'ew point -curve tormixtures at 20 lbs. gauge pressure, and the dew pointin this instancewill be approximately '14" F.

`By such al curve, itis also feasible to ascertain the` gallons ofcommercial ,butane per thousand cubic reet. equivalent to a known volume5 percentage of commercial butane, and to read rromthe'curve, thegallons perthousand direct.V

Like procedure may be followed in determiningthe caloriilc valuecorresponding toa certain commercial butane per cent in the iinishedgas.

Y It has been found by experimentation and test, that one gallon ofcommercial butane will vaporine to produce about 32 cubic feet of gas of3200 B. t. u. per cubic foot caloriilc value, and it is obvious that fordistribution and use, this gas maybe dilutedto reduce its heatcontentvto a point near the average'already in use by the industry, andto which the appliances are built and adapted. The caloriilc-value willbe assumed as 550 B. t. u.s per cubic foot in exempliiying the presentinvention.

The butane vapor can be y ted with any one oia large number of othegases, some having lower` caloriilc values,.such as blue water-ga`s, andproducer gas, and others or. air. The

a' large number ofdistinct advantages. Furl' thermore, accurate andautomatic proportioning 30 .machines are on the market, and may be usedto'mix commercial butane vapor'with air, givinga .resultant mixture oiextremely uniform caloriic value and constant specific gravity.

It is interesting to note that the behavior of commercial butanecoincides with thatpredicted vby calculations irom its physicalproperties.V

rlhis fact is borne out by the close checks between calculations an'dactual test results, both laboratory and commercial, withV respect todew points, caloriilc values, speciilc'gravities, vapor p etc. v Y Ithas been found that 17.2% of commercial Vbutane vapor (5.37 gallonsvperM) in 811'. gives sures encountered in standard gasplant or dismbutionpractice.

li any other gasthan air'is used as the base gas or diluting agent, bysubstituting the proper values, the resulting specic gravity andcalorific value can be readily calculated.

According to the most recent and the most authentic treatise on thesubject, (U. S. Bureau of Mines Bulletin No. 279, Limits ofinnammability of gases and vapors, by H. F. Coward and G. W.. Jones) thelower inammablity limit by volumes of butane in a mixture of butane andair, is 1.9%, and the higher limit is 8.5%. Since the percentage ofcommercial butane in a 550 B. t. u. air gas mixture is 17.2, it would benecessary to increase the amount of air to twice that of the mixed gasas normally made and distributed, before'reaching the upperinarnmability limit. i

Commercial butane contains a small 4amount of propane at one end, andaninsignificant amount of pentane at the other end. These two tendtocompensate each other, so that for the purpose of calculations, we canassurne that it is 100% (24H10. The theoretical amount of .air requiredfor complete combustion is then calculated from the equation:

C4H1o+6502+24.eN2- 4co2+5H2o+24.6Ni 6.5 volumes of O2, are', therefore,required to combine with one volume of commercial butane,

' or 6.5X4.7824=31.085 volumes of air, so that the percentagecomposition of a mixture that will give complete combustion is:l

Percent Commercial butane 3.117 Oxygen }air 20.258 Nitrogen. 76.625

Such a mixture has a specific gravity of 1.029,

anda caloriiic value of 99.74 B. t. u, per cubic' foot.

Similar calculations on the per cent of inerts present in thetheoretical air-gas mixtures for perfect combustion of carburetted watergas, coal gas, coke oven gas, oil -gas and natural gas, show thepercentage of inerts in the latter` gases to be only slightly less thanthat indicated in the commercial butane-air example above.

From thesforegoing it will be understood that the present invention isdesigned to take advantage of commercial butane or the equivalentthereof as the fuel component of manufactured gas, and intheaccompanying drawing, an apparatus is diagrammatically illustrated forthe purpose of disclosing theA invention in detail.

Referring to the drawing,

The figure is a flow diagram of a suitable apparatus for manufacturinggas from commercial butane and air or the like.

In accordance with the present invention, commercial butane in liquidcondition is shipped inv tank cars I, from'the point of production, tothe gas plant, and each of these tank cars is preferably provided withan eductioi pipe 2, extending to the bottom of the car, so that the carmay be unloaded into storage at the gas plant by the pressuredifferential method, thus eliminating the installation and maintenanceof pumps.

In case the pressure 1in the tank car is 'insumcient to cause the liquidto flow therefrom, it can be increased by any suitable means, such as asmall auxiliary gas compressor (not shown). Furthermore, each car may beequipped with coils (not shown), and in event steam or hot water isavailable, sufllcient pressure can. be maintained in the car toeffectively Atransfer the liquidi by heating the content, as the vaporpressure isv 6, set to open, say at lbs. pressure. It is also 5preferred to equip this tank with a valve controlled inlet 1, whichmaybe employed to introduce an odorizing agent; for commercial butane haspractically no odor.

Instead of passing the liquid butane from the 10 tank car into thestorage tank 5, it may be passed directly through a pipe line 8, td avaporizer 3, or when desired, butanes from the storage tank L5, may bepassed through the line 8, to the va.- porize. The line 8 may beequipped with educ- 15 tion check valves I I) and- II, and is alsopreferably lprovidedwith astrainer I2, and between the strainer and thevaporizer, a liquid regulator I8 isinterposed in the pipe line tomaintain a constant reduced pressure on the liquid in the vazo porizer.

The vaporizer may be constructed similar to a multitubular heatexchanger or condenser, and the water `or steam used for heatingpurposes, may be passed through the tubes of the vapor- 25 izer, whilethe liquid commercial butane will ow in the shell'space around thetubes. A small water heater '(not shown) will furnish sufficient heatinput to vaporze the liquid completely, as the latent heat required pergallon is only 830.30 B. t. u. The level at which the latent heat mustbe supplied by the vaporizer may be any suitable temperature in excessof the boiling point of the liquid commercial butane at the v'aporizerprsure, and may be as low as 40 or 50 F.

The heating medium may enter the top of the vaporizer through avalvedconduit Il, andmay be discharged from the bottom of the vaporizerthrough a valved conduit l5, or vice versa.

The liquid butane enters the vapon'zer at the 40 Apoint I8 near thebottom of the vaporizer, and

cates with a conduit I9 that is equipped with a 41,5

first vapor regulator 28. 'I'he vapors leaving the vaporizer aremaintained at a constant pressure by said regulator 20, and they owalong the conduit I9, past a manom'eter or pressure gauge 2I, a popvalve 22,and a meter 23, which are in- 5o teposed in the line I8. Thepipe I3 leads the vapors past a second vapor regulator 24, and into aproportioning machine 25, which functions to mix the vapors with aconstantly proportionate amount ofair or other base gas for dilutingpur- 55 Doses.

I usually set this machine soas to produce a gaseous mixture consistingof about 17% commercial butane, and about 83% air or other base gas. oc

The proportioning machine is provided with a discharge regulator 26 forthe finished gas, and is adapted to supply the said regulator with amixture of any desired caloric value. This machine is so constructedthat regulation of the ratio 65 of gas and air can be accomplished by,merely turning a valve, and once the machine is set forany definiteratio, it does not require subsequent adjustment.

From' the regulator 25, the finishedl mixture 70' flows through a pipe21 which is preferably provided at the point 28 with a recordingcalorimeter, and leads to a surge ltank 29. 'Ihe outlet pipe 38 of thelatter is provided with valved branches 3I and 32, and from the line 80,the nished gas '[5l is discharged into a low pressure holder' (notshown), a high pressure gas storage tank 33, or directly into the gasmains, as'the case may be. or as necessity requires. l

For accomplishing these\purposes, the branch 32 leads to a compressor 3lhaving a discharge most economical with this method of gas manufacture,unless a low pressure holder is already installed at a particular plant.This high pressure storage need not be-,used'for continuous service, butcancarry the olf-peak loads, thus cbviating the necessity forcontinuously 'operating the proportioning machine 25. Moreover, itprovides an emergency gas reserve, should electric power fail, or shouldthe proportioning machine or any of the equipment require repairs. In'any of these.contingencies,`.the gas can be passed to the mains througha valved pipe' 40 which leads to the line 31, and the latter isfurrushed with a reducing regulator Il, so'as to'reduce the pressure ofthe gas to that required in the mains.

The system preferably includes a line 42 which leads from both-storagetanks 5 and 33, back to the tank `car or liquid storage tank, and isequipped' with suitable valves so as to act as a tank car repressureline.

vapors formed in the unloading line 3 or storage tank 5, may be leddirectly through valved pi `43 and 44 respectively, into a conduit 45,which is also valved and meets the vapor conduit I8 at the point 43, sothat the evolved vapors can be passed to the proportioning maf Achinewithout going through the vaporizer 9. 'n

While one embodiment of the system has been' illustrated in theaccompanying drawing, .it-will be apparent to those skilled in the art,thatmany modifications thereof may be made without departing from thespirit of the invention.' v

A gaseous fuelconsisting of commercial butane and air, has the followingadvantages:

l. For practical purposes, it isa dehydrated gas, 'as the .only waterpresent'is the moisture in the diluent air at atmospheric temperature.If

this 'gas is compressed and stored at high pressure in the tank 33, thesmall amount of water would be partially condensed. It is feasible toatomize a amount of oil in the gas, as is ldone in natural gasinstallations, to lubricate the interior .of the mains.

2. No loss of caloriflc value occurs in the gas during transmission,asno condensation of the butanes takes place in the lines.

3. No gumming of lines, due to tar and naph thalenes is possible.

4. No purification isrequired, as commercialbutanes contain less than vegrains of organic sulphur per 1000 cubic feet of evolved vapor.

Itis true that the increased density of the gas will decrease thepipeline capacityythe spe'- cific gravityof a- 550 B. t. u. butane-airmixture being 1.163. As the pipe line capacity varies-the square root ofdensity of one gas over the density 'of other gas, the amount of twogasesofjdiiferent specific gravities handled by agiven distributionLsystem under the same operating conditions would be as the ratios ofthefsquare foot of their gravities. 'If the capacity with reference to a.65 gravity gas is compared, the pipe line capacity of the heavier gasis found to be 74.75%. Oifsetting this decreased capacity is the factthat no naphthalene, tar deposits or condensation tending to reduce thepipe line capacity,A will occur, and

' in the case of old used mains, the existing deposits will be graduallypicked up and carried with the gas to the point of combustion, and there-spect to calorific value and speciiic( gravity can be easilymaintained.

The. chief advantages of this system of manufacture are:

1. Exceptionallydow cost of plant installation.

2`. Greatly reduced labor cost.

3. Decreased capital charges, maintenance, repairs, etc.

4. Gas of unvarying quality within commercial limits.

5. Protable operation of small properties Where conventional plants haveheretofore not y. been justified.

. After a careful study of costs, it seems more economical toveinployhighpressure gasl storage tanks and a 'gas compressor with a semi-highpressure distribution system than to use a holder and a low pressuresystem. Thecost of the cc'm- 410 presser-and high pressure storage willnot be as great as that o'f the holder, and the high pressuredistribution system cost will be loweron account of the decreased linesizes. It is possible to put gas directlyinto the service mains ,fromthe discharge of the Aconventional proportioning machine, as'long as thedistribution pressure is less than about three pounds, at the same timecarrying filled high pressure storage tanks as an emergency finished gasreserve.

The system has been disclosed in connection with commercial butane asthe fuel component of the finished gas mixture, but'it will', of course,be' understoodv that other normally gaseous hydrocarbons maybesubstituted therefor, but it is'ordinarily preferred to use commercialbutane as there is a'n abundance of raw material available from whichcommercial butane may be inexpensively extracted.

Commercial propane is equally useful as a fuel in the process described,even though it may have -f a certain disadvantage from theliquidlshipping. handling and storage'standpoint, on account of the factthat its vapor pressure (about 120 pounds gauge\a t '10? E.) isconsiderably higherthan that o f commercial butano. On the other hand,the use of commercial propane, propane-bulgarie mixs, or even themorevolatileparaiiin hydrocarbons, offers substantially lower dew points innished gas of any certaincaloriflc value, than the' dew points obtainedwhen using commercial butano.

.While I prefer to employ vparafiin hydrocarbons as-tlie fuel element ofmy gas, it is manifest that I may use normally gaseous hydrocarbonswhich are not strictly parailin hydrocarbons, for example, renery stillgases Acontaining propylene, ethylene, unsaturated hydrocarbons,aromatic hydrocarbons, napthenes, etc.

Furthermore, I desire it to be understood that in some cases, the fuelmay be passed from the tank car or storage tank I, to the proportioningmachine 25, without using the vaporizer. In such a case, a heating coilin the tank car or storage tank, can furnish the heat of vaporization,or in the case of propane or other relatively volatile hydrocarbons,latent heat will flow into the tank from the surrounding atmosphere, andwill thus cause` vaporization.

From the foregoing it is believed that the construction of theapparatus, steps of the process, and the advantages of the system may bereadily understoodl by those skilled in the art.

What is claimed and desired to be secured by Letters Patent is:

1A. Apparatus for producing gaseous mixtures, comprising meansfoi-storing a fuel gas in liquefied condition, a vaporizer, a conduitfor leading liquefied fuel gas to the vaporizer from said storage means,a proportioning machine for mixing the fuel with a base gas, a secondconduit for leading the fuel gas from the vaporizerto the proportionin'gmachine, pressure regulators interposed in said conduits for governingthe pressure of the fuel gas entering and leaving the vaporizer, and avapor conduit leading from the storage means to the second conduit fordischarging fuel gas vapor directly into the second conduit between thevaporizer and proportioning machine.

2. An apparatus for producing gaseous mixf tures, comprising a firstpressure tank for use in transportingl'liquefled petroleum gas, a secondpressure storage tank for 'storing said gas in liqueed condition,.aconduit leading from the bottom of the, first tank to the second tankfor transferring the gas in liqueed condition from the first to thesecond tank, means for vaporizing liquefied gas from either of saidtanks,

means for proportioning the vaporzed gas and a base gas and for mixingthe same, a third pressure storage tank for the mixture, means forcompressing the mixture and for introducing the same into the third tankunder pressure,

' and valve controlled conduits placing the second and third tanks incommunication with the first tank for leading pressure gases from thesecond and third tanks into the first tank.

3. An apparatus for producing gaseous mixtures, comprising a pressurestorage chamber adapted to contain liquefied gas, a vaporizer forcompletely vaporizing said gas, a conduit for leading liquefied gas fromthe storage chamber to the vaporizer, an automatic proportioning machinefor proportioning air and gas at a constant ratio, a conduit for leadingall of the vaporsfrom the vaporizer to the proportioning machine, avapor regulator interposed in the last mentioned conduit for maintainingthel pressure of the'vapo'rs substantially constant, means forming partof the proportioning machine for mixing the vapors with air, and meansfor discharging the mixture from the proportioning machine.

4. An apparatus for producing gaseous mixtures, comprising a pressurestorage chamber vaporizer, a conduit leading from the storage chamber tothe vaporizer, an automatic proportioning machine for proportioning abase gas and Ehe first mentioned gas at a constant ratio, a conduit forleading all of the vapors from the vaporizer to the proportioningmachine, a vapor regulator interposed in the last mentioned con- 1 duit,means forming part of the proportioning machine for mixing the vaporswith a base gas,

Vmeans for discharging the mixture from the ROSSWELL W. THOMAS.

adapted to contain a liquefied petroleum gas, a

